Applying gravity only when not on floor?

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1

Godot Version

Godot Engine v4.6.stable

Question

Hi!

In a lot of the examples I checked about CharacterBody3D, I’ve seen that the gravity is applied only when “is_on_floor()” returns false.

if not body.is_on_floor():
	velocity += gravity * delta

Is it really the way to do it? Just a small optimization?
For most common use cases, this seems right and is working well, but in mine, it triggers an issue when moving on a curved surface with my custom gravity system (actually small planets, my gravity system updating CharacterBody3D.up_direction): “is_on_floor()” oscillate between true and false. I expected the same problem when walking down on slopes or on curved surface in static gravity conditions, but I didn’t notice anything.

I initially though of a problem with snapping function but I haven’t found a lot of information about it and couldn’t solve my problem that way.
What actually solved it without triggering any other issue is removing “is_on_floor()” check and simply applying gravity every frame.
So in practice, I no longer have any issue, everything is working as expected, but I’m questioning that practice or the way I solved my issue.

Is it wrong applying gravity that way? Did I miss something about the snapping function?

2

a code that works ; is the right code :moai:

for oscillation between true and false ; you should increase the gravity ; when your player is passing a curved floor . it can handle by a Raycast .

3

Yes, I guess you’re right. It’s more a discussion to better understand this and make sure I didn’t get something wrong than a request for help :slightly_smiling_face:

In very strong gravity condition, the character barely jumps, stick to the surface, but “is_on_floor” state still oscillate when moving.

4

Character bodies have a property for the “up” direction that determines what is a floor, wall and ceiling. For 2D see – CharacterBody2D — Godot Engine (stable) documentation in English and there’s a similar property for 3D.

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5

Yes, my script is actually updating that up_direction property. I don’t think that is the issue.

6

You’re encountering a similar problem to what occurs with is_on_wall(). In that case, it is only true if the player is moving towards a wall. You have an edge case. There are two options. You can make gravity always apply like you did. Or, you can use a RayCast2D opposite of the UP direction to determine when to apply it.

I recommend considering using the Area2D gravity override properties. Then you can just use get_gravity() and apply it. What you’re doing is likely not causing the problem you’re seeing, but it might be, and it might cause other unforeseen problems in the future.

7

I’m working in 3d, but it is exactly what I’m doing. Are the Area2D/Area3D gravity override system supposed to automatically update the up_direction? I maybe should make another try not updating it manually.

Anyway, if there isn’t any problem with applying gravity all the time, I think I’ll stick with that solution.

Thanks you for your answers

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8

Sorry, my mistake. Works the same for 3D.

I took a look at up_direction again and it looks like there’s nothing wrong with updating it. It determines what is a floor, wall and ceiling. Personally, I use is_on_ceiling() instead of inverting it, but it makes sense with what you described.

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